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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Nick Crews <ncrews@chromium.org>
Cc: linux-usb@vger.kernel.org,
	Enric Balletbo i Serra <enric.balletbo@collabora.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Daniel Kurtz <djkurtz@google.com>
Subject: Re: Policy to keep USB ports powered in low-power states
Date: Tue, 13 Aug 2019 08:02:49 +0200
Message-ID: <20190813060249.GD6670@kroah.com> (raw)
In-Reply-To: <CAHX4x86QCrkrnPEfrup8k96wyqg=QR_vgetYLqP1AEa02fx1vw@mail.gmail.com>

On Mon, Aug 12, 2019 at 06:08:43PM -0600, Nick Crews wrote:
> Hi Greg!

Hi!

First off, please fix your email client to not send html so that vger
does not reject your messages :)

> I am working on a Chrome OS device that supports a policy called "USB Power
> Share," which allows users to turn the laptop into a charge pack for their
> phone. When the policy is enabled, power will be supplied to the USB ports
> even when the system is in low power states such as S3 and S5. When
> disabled, then no power will be supplied in S3 and S5. I wrote a driver
> <https://lore.kernel.org/patchwork/patch/1062995/> for this already as part
> of drivers/platform/chrome/, but Enric Balletbo i Serra, the maintainer,
> had the reasonable suggestion of trying to move this into the USB subsystem.

Correct suggestion.

> Has anything like this been done before? Do you have any preliminary
> thoughts on this before I start writing code? A few things that I haven't
> figured out yet:
> - How to make this feature only available on certain devices. Using device
> tree? Kconfig? Making a separate driver just for this device that plugs
> into the USB core?
> - The feature is only supported on some USB ports, so we need a way of
> filtering on a per-port basis.

Look at the drivers/usb/typec/ code, I think that should do everything
you need here as this is a typec standard functionality, right?

thanks,

greg k-h

       reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CAHX4x86QCrkrnPEfrup8k96wyqg=QR_vgetYLqP1AEa02fx1vw@mail.gmail.com>
2019-08-13  6:02 ` Greg Kroah-Hartman [this message]
2019-08-14 20:12   ` Nick Crews
2019-08-14 21:20     ` Greg Kroah-Hartman
2019-08-15  0:08       ` Nick Crews
2019-08-15 23:42         ` Duncan Laurie
2019-08-16  9:12           ` Greg Kroah-Hartman
2019-08-16 17:02             ` Duncan Laurie
2019-08-27 15:29               ` Enric Balletbo i Serra
2019-08-29 22:10                 ` Nick Crews
2019-09-02 20:16                   ` Pavel Machek

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